Combined resistor and shunt switch



June 7, 1938. I. E. MCCABE 2,120,056

COMBINED RESISTOR AND SHUNT SWITCH Original Filed July 31, 1933 IN VENTOR. jKA y 5 6/455 ATTORNEY.

Patented June 7, 1938 r UNITED STATES PATENT OFFICE COMBINED RESISTOR AND SHUNT SWITCH Ira E. McCabe, Chicago, Ill.

Original application July 31, 1933, Serial No. 683,037. Divided and this application February 11, 1935, Serial No. 5,931

Claims. (Cl. 20148) This invention. relates to improvements in To avoid damage, or unnecessary abuse to reswitching systems and more particularly to a versing motors, or equipment operated thereby; it combined resistor and shunt switch for use in is often necessary or desirable to provide a delay such a system. This application is a division of between the opening of the running circuit and 5 this applicants prior copending application Serial the closing of the reversing circuit and vice versa. 5 No. 683,037, filed July 31, 1933. The control of such motors is usually accom- It is an object of this invention to provide an plished through remote control switches which electric switch so constructed that when the ciropen and close the motor circuits and additional cult is first established therethrough to include mechanism is required to provide the delay necesan electrical resistance in said circuit and upon sary between the closing of the motor circuit and 10 operation of the switch to shunt out the resistthe operation of the motor. ance and allow the full current to pass there- The additional mechanism is interposed bethrough. It is a further object of this invention tween the source of the current and the motor to include a resistor in a mercury tube switch and caused to function upon the opening andwhich willbe shunted out when the switch has closing of the remote control switch to immedi- 15 been tilted to cause the mercury to contact the ately open the circuit to the motor and thereelectrodes thereof. after allow a period for slowing up or stopping Such combined resistor and shunt switches are of the motor before closing the reversing circuit, of advantage when delayed action is desired in to provide always a positive delay in the breakcontrolling the operation of an electric motor ing of one motor circuit and making the reversing 20 and more particularly in connection with concircuit, following the operation of the remote controlling reversing motors as disclosed in said trol switch, regardless of how rapidly the control parent application. switch is caused to operate.

With these and other objects in view, reference It is preferable in the delay switch operating is made to the accompanying sheet of drawings mechanism to use the repulsion relay such as dis- 25 which illustrates an embodiment of this invenclosed in this applicants co-pending application, tion with the understanding that detail changes Serial No. 508,185, filed January 12, 1931, now may be made without departing from the scope Patent No. 1,973,925 of September 18, 1934, which thereof. 1 is adaptable for use with either alternating or In the drawingdirect current or the relay disclosed in this ap- 30 Flgure 1 is a view partly in front elevation and plicants co-pending application, Serial No. partly in diagram, illustrating an application of 500,747, filed December 8, 1930, which may be of this invention asdisclosed in said parent applithe transformer type permitting the use of low cation. voltage remote control equipment, and in con- Figure 2 is a view in longitudinal vertical cennection with the relays to employ an electrical 35 tral section of this improved switch, shown in resistor in the control circuit. The resistor conthe open position with parts shown in side elevatemplated may be any of the resistance elements,

tion. which offers great resistance to the passage of Figure 3 is a view similar to Figure 2 showing electric current therethrough when cold, but as this improved switch in closed position. its temperature increases, due to the passage of 40 Figure 4 is a top plan view of Figure 1. current therethrough its resistance decreases For a better understanding of the advantages until a large amount of current is passable. Such and peculiar construction of this improved comelements are known in the art and one known bined resistor and shunt switch, it is deemed adas Durhy, an electric furnace product having as visab'le to first briefly describe a practicable comits base silicon carbide with a very high dissocia- 46 mercial application of this novel switch before tion temperature, is manufactured by the Globar defining its peculiar construction. With this ob- Corporation of Niagara Falls, New York. ject in view, reference is made to Figure 1 of the The control for a. reversing motor shown in drawing which shows in diagram the application Figure 1 includes an electric motor M and two re- 50 of this switch in controlling the operation of a lays comprising a rectangular core C with a sta- 50 reversing motor, as more specifically disclosed in tionary primary coil P secured to the center of this applicant's parent application, Serial No. the upper leg thereof with movable secondary 683,037. filed July 31, 1933, with the understandcoils S mounted upon the same leg on each side ing that by so doing the use of this invention is of the stationary coil P. The switch carrying in no way limited to this single use. arms I are pivotally mounted at I to the lower leg of the core C and are each secured at their upper ends to their respective secondary coils. The arms I] are extended downward on opposite sides of the lower leg to which they are pivoted and the lower ends of each arm supports a motor switch MS and a shunt switch SS, as shown, so that the weight of said switches normally maintain the coils S in contact with the coil P.

The binding post is connected to one side L of the source of commercial current and also to one winding of the primary coil the other wire of which is connected through the binding post 3 to the return line L commercial current. The binding post 2 is connected through the motor switch operated by the left hand coil S to binding post i and thence through the motor to operate it in the forward direction to the binding post 3. The binding post 22 is also connected through the motor switch MS on the right hand side to the binding post 5 and thence through the motor to operate it in reverse direction to binding post 3. in this form, one end of the windings of each of the secondary coils S are connected through their respective shunt switches SS to binding post ii and from thence to the remote control switch BC. The contact I adapted to be engaged by the remote control switch is connected to the other end of the winding of the secondary coil upon the right of the primary coil and the contact t adapted to be en- 'gaged by the remote control switch is connected to the other end of the secondary coil upon the left of the primary coil.

In this form, the shunt switches SS are identical and each one is a mercury tube switch especially constructed to act as both a resistance element and as a shunt switch, as shown in Figures 2, 3 and 4. As shown, the lower terminal 9 is provided with an ofiset I0 adapted to engage one end of the resistor element R and the upper ter- -minal H is brought down to contact the other end of the resistor R and hold the same firmly in position between the two terminals at the bottom of the mercury tube switch. The resistor is provided with metal caps RR to which the terminals are welded. By this construction when the remote control switch opens the circuit through a secondary coil, the weight of the switches carried thereby returns it to contact with the primary coil and opens both of said switches, so that when the remote control switch reestablishes the circuit through the secondary coil, the current passes through the resistor in the open shunt switch causing a delay in the movement of the secondary coil until the resistor has increased sufiiciently in temperature to allow sufllcient current to pass therethrough to repel said secondary coil, whereupon the motor switch and shunt switches are closed. The closing action of the shunt switch causes the mercury 02 therein to contact the terminals '9 and i I to establish the circuit through the resistor R and as the switch is tilted the mercury itself not only shunts out the resistor R but as it submerges the resistor R also has a cooling effect and accelerates the reduction in temperature of the resistor so that upon rapid switching of the remote control BC the delay, resulting from the heating of the resistor, will not be shortened.

What I claim is: p

i. A combined resistor and shunt switch including an envelope having terminals sealed in the walls thereof, an electrical resistor having a 1 negative temperature coefficient interposed between the terminals to be always connected in circuit therewith, and a movable body of conducting fluid which, in one position of the switch, moves away from the resistor and terminals to be completely out of contact therewith, and, in another position of the switch moves to submerge the resistor and shunt it.

2. The structure of claim 1 in which the terminals are engaged by the fluid before the resistor is submerged.

3. The structure of claim 1 wherein the terminals are simultaneously engaged and the circuit closed by the conducting fiuid before the fluid engages the resistor.

4. In a mercury tube switch, a sealed glass envelope containing a movable body of mercury,

electric terminals sealed in one end thereof one above the other, the upper terminal bent at an angle within the envelope to endin the same plane and in line with the end of the lower terminal, said lower terminal offset within the en velope adjacent the wall thereof, and an electric resistor having a negative temperature coefficient interposed between said oifset terminal and end of the upper terminal to be always in circuit therewith, whereby when the mercury is contained in one end of the envelope, it is out of contact with the said terminals and resistor and upon flowing into the other end, the mercury shunts the resistor and reduces its temperature.

5. A combined resistor and shunt switch including a tiltable mercury tube switch containing a body of mercury and two spaced apart terminals extending thereinto normally out of con- 1 mercury upon tilting the switch in one direction and be submerged and shunted by said mercury upon tilting the switch in the other direction.

IRA E. MCCABE. 

